chen gong wrote:
On 2010-3-11 16:07, ykzhao wrote:
On Thu, 2010-03-11 at 10:18 +0800, Prarit Bhargava wrote:
Yes. The nehalem processor has the integrated memory controller. But it
is not required that the hot-added memory should be onlined before
bringing up CPU.
I do the following memory-hotplug test on one Machine.
a. Before hot plugging memory, four CPUs socket are installed and
all the logical CPU are brought up. (Only one node has the memory)
b. The memory is hot-plugged and then the memory is onlined so that
it can be accessed by the system.
In the above testing case the CPU is brought up before onlining the
hot-added memory. And the test shows that it can work well.
That doesn't work when you have multiple nodes AFAICT. The cpus do not
come into service because of a lack of memory on the node.... per node
allocations will fail.
In the test the system has multiple nodes. The reason is that the cpu
without memory can turn to other node and allocate the memory.
I agree with Yakui. The memory and CPU are irrelevant in some way. CPU can
get memory from other nodes if it hasn't local memory, though for now it has some issues.
Andi is working on it now (http://lkml.org/lkml/2010/2/3/343)
Right -- I'm working with Andi on this to get RHEL working. So I have
his slab patches, etc.. That's one of the reasons it isn't working
right now.
BTW, how about using UDEV rules to do this operation. It looks more smooth. I know some
Novell guy is working on it.
I was thinking about that, but the CPU comes online automatically, so
why not memory? It seems to be a discrepancy between the two. And ...
the two of you still aren't considering the obvious performance hit
which I would think makes this a must have.
P.
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